#include<stdio.h>
#include<math.h>

double H(double x,int n);
int main(void)
{
	double x;
	int n;
	scanf("%d %lf",&n,&x);
	printf("%.2lf",H(x,n));
	return 0;
}

double H(double x,int n)
{
	if(n==0)
	{
		return 1;
	}
	if(n==1)
	{
		return 2*x;
	}
	if(n>1)
	{
		return (double)2*x*(H(x,n-1))-(double)2*(n-1)*(H(x,n-2));
	}
}
